Thermally efficient CCD camera housing

ABSTRACT

A system and method of cooling a CCD camera may employ a composite material housing design that allows the cold side of a TEC to be mounted relatively close to the CCD and the hot side of the TEC to be isolated from the housing cavity in which the CCD resides. An efficient heat transfer path may facilitate cooling the CCD to a predetermined or selected operating temperature and isolate the CCD from the heat loads generated by operation the TEC.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. provisionalapplication Ser. No. 60/430,988, filed Dec. 4, 2002, entitled “THERMALLYEFFICIENT CCD CAMERA HOUSING.”

FIELD OF THE INVENTION

Aspects of the present invention relate generally to cooled CCD cameras,and more particularly to a thermally efficient CCD camera housing.

DESCRIPTION OF THE RELATED ART

The design of low light detection charge-coupled device (CCD) camerastypically requires the CCD to be operating at low temperatures (e.g.,from about 0° C. to about −40° C.). To achieve such low operatingtemperatures, typical systems employ a thermoelectric cooling (TEC)component coupled in some manner to the CCD.

A conventional TEC has both a cold surface and a hot surface; the hotsurface (operably coupled to a heat sink) generally must be maintainedat or near a predetermined or target temperature to ensure that the coldsurface (operably coupled to the CCD) may provide optimum effectivenesswith respect to cooling the CCD. Even when the TEC is operating asintended within the appropriate parameters, conventional TEC design isrelatively inefficient. For example, to maintain a desired CCD operatingtemperature, it may be necessary for a conventional system to supply asmuch as 25 Watts of energy to the TEC to cool an ambient heat load of 4Watts. In this case, the total amount of heat that must be removed fromthe system may be expressed as:4 Watts+25 Watts=29 Watts

where 4 Watts represents the ambient load and 25 Watts represents thepower input to the TEC necessary to provide the 4 Watts of ambientcooling.

Another requirement for a cooled CCD camera is that the environmentaround the CCD be maintained at very low moisture or relative humiditylevels. At low operating temperatures, atmospheric or other moisture inor around the CCD housing may condense and freeze, causing imaging andreliability problems. Accordingly, CCD housings generally require orsubstantially benefit from an environmentally tight seal to preventmoisture contamination and attendant imaging difficulties. Additionally,a non-porous material is generally preferred for such CCD housings,which is why aluminum is a popular choice for these applications.Aluminum is also a good heat conductor, however, which means that analuminum housing surrounding the CCD may not be effective in isolatingthe CCD from either ambient or TEC generated heat.

Conventional systems, therefore, are generally deficient at least withrespect to the problem of transferring ambient heat loads and heatgenerated from the TEC away from the CCD without “re-circulating” suchheat back into the proximity of the CCD. Additionally, as noted above,an environmentally tight seal around the CCD generally must bemaintained to avoid moisture build-up on the CCD.

In an attempt to overcome some of the above-noted deficiencies, somecooled CCD system designs mount the TEC physically away from the CCD andtransfer heat from the CCD via a relatively long coupling mechanisminterposed between the CCD and the TEC. This strategy helps to positionany heat generated by the TEC at a desired distance from the CCD, andthus to isolate the CCD from that particular heat source. On the otherhand, this arrangement generally results in inefficient heat transferbetween the CCD and the cold side of the TEC; in many cases, inefficientheat transfer characteristics are caused by an increased thermalresistance associated with the elongated coupling mechanism. Thermalresistance increases at every interface between coupling mechanismcomponents, for example, and is also directly related to the distanceover which the heat travels. Accordingly, for a given TEC, coolingefficacy and efficiency generally vary directly with proximity to theCCD.

Alternatively, some CCD system designs mount the cold side of the TECdirectly to the CCD; in these arrangements, the hot side of the TEC isgenerally mounted or attached directly to the CCD housing. As statedpreviously, the CCD housing is typically aluminum (which has highthermal conductivity) and generally serves as a heat sink for the TEC.On the other hand, since the hot side of the TEC is mounted to the CCDhousing, these component arrangements generally result in undesirableheat transfer to the housing itself. As a consequence, since the CCD isalso constructed from, or directly mounted on, the housing, the CCDcavity heats up as well.

Rising temperatures in the CCD cavity create more of an ambient heatload, which in turn results in decreased cooling efficiency for the CCD.The foregoing problem is compounded by the fact that heat tends to flowto the coldest regions of the system, which in this case may be the CCD.This scenario can also result in a temperature/time response curverelative to the CCD that is difficult to predict as the CCD initiallycools, then starts to warm up when the camera housing becomes “heatsaturated.”

SUMMARY

Embodiments of the present invention overcome the above-mentioned andvarious other shortcomings of conventional technology, providing athermally efficient housing for use in conjunction with a CCD camera orsimilar device. A system and method operative in accordance with someembodiments, for example, may employ a composite material housing designthat allows the cold side of the TEC to be mounted relatively close tothe CCD and the hot side of the TEC to be isolated from the housingcavity in which the CCD resides. An efficient heat transfer path maysimultaneously facilitate cooling the CCD to a predetermined or selectedoperating temperature and isolate the CCD from the heat loads generatedby operation the TEC.

In accordance with some embodiments, for example, a method of cooling acharge-coupled device comprises coupling the charge-coupled device to acold side of a thermoelectric cooling device, coupling a hot side of thethermoelectric cooling device to a transfer plate, mounting the transferplate to a thermal barrier, and coupling the transfer plate to a heatsink.

As set forth in more detail below, such a method may optionally furthercomprise interposing a spacer between the charge-coupled device and thecold side of the thermoelectric cooling device. In embodiments employingsuch a spacer, the interposing operation may comprise selectivelydimensioning the spacer to maximize a surface area of contact betweenthe charge-coupled device and the cold side of the thermoelectriccooling device. Additionally or alternatively, the interposing operationmay comprise selectively dimensioning the spacer to position the hotside of the thermoelectric cooling device in a predetermined locationrelative to the charge-coupled device.

Some methods described herein may further comprise selectively applyinga conformal coating to at least one of the transfer plate, the thermalbarrier, and an interface between the transfer plate and the thermalbarrier. In accordance with some embodiments, such selectively applyingmay comprise providing an environmentally tight moisture barrier withthe conformal coating.

The foregoing methods may further comprise cooling the hot side of thethermoelectric cooling device. It will be appreciated that, in someinstances, this cooling comprises transferring heat generated by thethermoelectric cooling device from the charge-coupled device.

The above-mentioned operation of mounting the transfer plate to athermal barrier may comprise attaching the transfer plate to an epoxylaminate material, to a ceramic material, or to some other material orstructural element which fails to conduct heat or does so only at aselected or predetermined rate. In accordance with some methods, thismounting operation comprises isolating heat generated by thethermoelectric cooling device from the charge-coupled device.

In accordance with other exemplary embodiments, an apparatus comprises acharge-coupled device mounted in a housing, a thermoelectric coolingdevice having a cold side and a hot side—the cold side coupled to thecharge-coupled device—a heat sink, and a transfer plate coupling the hotside of the thermoelectric cooling device to the heat sink in a heattransfer relationship; the transfer plate mounted to a thermal barrieroperative to prevent heat transfer between the thermoelectric coolingdevice and the housing.

The foregoing apparatus may optionally further comprise a spacerinterposed between the charge-coupled device and the cold side of thethermoelectric cooling device. In some instances, such a spacer may beselectively dimensioned to maximize a surface area of contact betweenthe charge-coupled device and the cold side of the thermoelectriccooling device. Additionally or alternatively, the spacer may beselectively dimensioned to position the hot side of the thermoelectriccooling device in a predetermined location relative to thecharge-coupled device.

Some apparatus configured and operative in accordance with the presentdisclosure may further comprise a conformal coating applied to at leastone of the transfer plate, the thermal barrier, and an interface betweenthe transfer plate and the thermal barrier. Embodiments are describedwherein such a conformal coating provides an environmentally tightmoisture barrier for the coated structural elements, the interfacetherebetween, or both.

By way of example, the thermoelectric cooling device may be embodied inor comprise a Peltier cooling device. As set forth in more detail below,embodiments of the foregoing apparatus may be fabricated wherein thetransfer plate is constructed of a heat-conducting metal. Similarly, analternative is described wherein the spacer is constructed of aheat-conducting metal. Conversely, in the exemplary embodiments, theforegoing thermal barrier is constructed of an epoxy laminate material,a ceramic material, or some other material which fails to conduct heator does so only at a selected or predetermined rate.

The foregoing and other aspects of various embodiments of the presentinvention will be apparent through examination of the following detaileddescription thereof in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified cross-sectional diagram illustrating oneembodiment of a CCD apparatus.

FIG. 2 is a simplified plan diagram of the embodiment of a CCD apparatusdepicted in FIG. 1.

FIG. 3 is a simplified perspective diagram illustrating anotherembodiment of a CCD apparatus.

FIG. 4 is a simplified flow diagram illustrating the general operationalcharacteristics of one embodiment of a CCD cooling method.

DETAILED DESCRIPTION

Turning now to the drawing figures, FIGS. 1 and 2 are simplifiedcross-sectional and plan diagrams, respectively, illustrating oneembodiment of a CCD apparatus. FIG. 3 is a simplified perspectivediagram illustrating another embodiment of a CCD apparatus. Apparatus100 may generally comprise an insulated housing 110 defining a CCDcavity 111 in which a CCD camera 199 or other device, as well asattendant electronics or associated circuitry such as printed circuitboard (PCB) 198, may be mounted. As indicated in FIGS. 1 and 3,apparatus 100 further comprises or incorporates a thermoelectric cooler(TEC) 130 operably coupled to CCD 199 as set forth in more detail below.

As is generally known and understood in the art, TEC 130 may be embodiedin or comprise a Peltier cooling device, i.e., a solid-state heatpumping apparatus which operates on direct current (DC) power. TEC 130may comprise a hot side 131 operably coupled to a heat sink 105 and acold side 133 operably coupled to CCD 199.

As illustrated in FIGS. 1 and 3, some embodiments may further comprise aspacer or transfer plate 180 of a suitable size and material interposedbetween hot side 131 of TEC 130 and heat sink 105; it will beappreciated that transfer plate 180 may couple hot side 131 and heatsink 105 in a heat transfer relationship, i.e., conducting heat to heatsink 105 at a desired or predetermined rate. In that regard, transferplate 180 may be fabricated of material having heat transfercharacteristics suitable to accommodate cooling requirements ofapparatus 100. In some embodiments, for example, transfer plate 180 maybe fabricated of copper, brass, or aluminum, though other materialsexhibiting appropriate heat transfer characteristics may also be used.The specific material selected for transfer plate 180 may be affected orinfluenced by the dimensions (such as overall size and thickness) oftransfer plate 180 itself, the dimensions, shape, and efficiency of TEC130, heat sink 105, or both, as well as other factors which may vary inaccordance with design specifications of apparatus 100.

In the exemplary embodiments of FIGS. 1 and 3, a transfer plate orspacer 117 may be interposed between cold side 133 of TEC 130 and CCD199. Spacer 117 may generally be configured and operative to couple coldside 133 and CCD 199 in a heat transfer relationship, i.e., spacer 117may conduct heat away from CCD 199 during use. In that regard, materialfor spacer 117 may be selected in accordance with heat conductivitycharacteristics appropriate for system requirements. While spacer 117may be copper, aluminum, or brass, for example, other materials havingsuitable heat transfer properties may also be used. As with transferplate 180, the specific material selected for spacer 117 may beinfluenced by the dimensions of spacer 117 itself, the dimensions,shape, and efficiency of TEC 130, the dimensions and desired operatingtemperature of CCD 199, as well as other considerations which may varyas a function of the overall design characteristics of apparatus 100.

While spacer 117 generally lengthens the heat path by increasing thedistance and material interfaces between CCD 199 and cold side 133 ofTEC 130, spacer 117 may improve overall cooling efficiency andfacilitate isolation of TEC 130, and heat generated thereby, from CCD199 and cavity 111 substantially as set forth below. As best illustratedin FIG. 1, spacer 117 may project or extend through PCB 198 andsimultaneously provide a large contact area with respect to cold side133 of TEC 130. Additionally, spacer 117 may be dimensioned tofacilitate or to allow positioning of hot side 131 of TEC 130 in asuitable location for mounting (through transfer plate 180) onto athermally insulated structure, or “thermal barrier,” such that heatgenerated by operation of TEC 130 is not re-circulated back to cavity111, in general, nor to CCD 199, in particular. It will be appreciatedthat spacer 117 may be omitted in some embodiments where othercomponents are suitably sized and dimensioned.

With respect to isolating heat generated by TEC 130, housing 110 maygenerally be embodied in or comprise three portions, each respectivelyconstructed of different materials: a portion constructed of aluminum ora similar material (reference numeral 119, e.g., for enclosing CCDcavity 111); a portion constructed of copper or a similar materialemployed as a transfer plate 180 (e.g., for mounting TEC hot side 131);and a portion constructed of epoxy-glass laminate, ceramic, or a similarinsulating material acting as a thermal barrier (reference numeral 118,e.g., for mounting transfer plate 180 and insulating or isolating CCDcavity 111 from the heat path). The copper and epoxy laminate are,respectively, highly efficient conductors and insulators of heat;combined as set forth herein, these materials may create an efficientthermal path for directing heat away from CCD 199.

During operation of apparatus 100, heat travels from CCD 199 and TEC 130into transfer plate 180 (constructed of or comprising, for example,copper as noted above) and out of the camera system via heat sink 105(attached or otherwise coupled to transfer plate 180 in a heat transferrelationship). As generally known in the art, the foregoing coolingprocess may be facilitated by air or other cooling gas circulated, forexample, by one or more fans or fan assemblies 120. In accordance withthe arrangement depicted in FIGS. 1 and 3, transfer plate 180 isattached or coupled to an epoxy-glass laminate thermal barrier 118,rather than to the aluminum portion 119 of housing 110. Accordingly,heat may be prevented from raising the temperature of housing 10 itselfand from re-entering CCD cavity 111.

It will be appreciated that the high-efficiency exemplary designs ofFIGS. 1 and 3 allow for the use of a smaller, less expensive TEC 130 andassociated power supply (not shown) than would otherwise be required.

As previously discussed, suitable material for various portions ofhousing 110 may be selected as a function of thermal characteristics andheat transfer design considerations. For example, from a heat transferperspective, an insulator such as epoxy-glass laminate 118 (or otherinsulating material such as various ceramics) may be suitable toinsulate CCD cavity 111. In some embodiments employing epoxy-glassinsulation, this laminate may be porous; in fact all interfaces betweensuch an insulating laminate and transfer plate 180 (i.e., mount for hotside 131 of TEC 130) may be porous. In some instances, such porosity mayeventually lead to moisture migrating into cavity 111. As notedgenerally above, such moisture contamination may degrade the imagingcapabilities of CCD 199, and may potentially damage CCD 199 or othercircuitry 198 within cavity 111.

In accordance with the embodiments illustrated and described above withreference to FIGS. 1 and 3, the structural arrangement and functionaldesign of apparatus 100 may generally utilize a type of conformalcoating (not shown) applied to the entire composite assembly (i.e.,transfer plate 180, laminate materials 118, and aluminum 119 materialsemployed for housing 110) or selected portions thereof. In someembodiments, for example, epoxy-laminate 118 or an insulating structureof similar material and transfer plate 180 may be bolted, welded, fused,adhered, or otherwise joined, coupled, or attached prior to or inconjunction with application of a conformal coating and sealing layer;these two components, and the junction therebetween, may be coated andsealed with a conformal coating as set forth above. The coating processmay remove moisture from, and prevent moisture from penetrating, thematerials selected for the various components of housing 110, andadditionally may seal exposed surfaces and the component interfaces.

In particular, such a coating may seal (i.e., provide an environmentallytight vapor or moisture barrier for) epoxy-laminate portion 118,transfer plate 180, and the interface between these structuralcomponents. As a consequence, apparatus 100 may generally embody alow-porosity assembly configured and operative to provide optimum heattransfer. Various conformal coating materials and methods for applyingsame are generally known in the art. The present disclosure is notintended to be limited by the material selected for such a coating, norby any specific techniques employed in its application.

The combination of materials in the design of housing 110 may create athermally efficient assembly that is optimized for heat conduction, heatinsulation, and minimal porosity. Accordingly, CCD 199 may be maintainedat colder operating temperatures with smaller, less powerful TECdevices.

FIG. 4 is a simplified flow diagram illustrating the general operationalcharacteristics of one embodiment of a CCD cooling method. As indicatedat block 401, a CCD camera may be coupled to a spacer; as set forth indetail above, such a spacer may be suitably or selectively dimensionedto position the hot side of the TEC in a predetermined or selectedlocation relative to the CCD (e.g., facilitating isolation of heatgenerated by the TEC), and may further be configured and operative toprovide a large surface area of contact with the cold side of a TEC;maximizing this surface area of contact may facilitate heat transferfrom the CCD. In that regard, the spacer may be coupled to the cold sideof the TEC as indicated at block 402.

The hot side of the TEC may be coupled to a transfer plate (block 403)having appropriate heat transfer characteristics. In the embodimentsillustrated and described in detail above with reference to FIGS. 1 and3, such a transfer plate may be coupled to a heat sink (block 405) andmounted to an insulated thermal barrier (block 404) rather than to analuminum or other heat-conductive portion of the CCD housing. As setforth above, mounting (block 404) the transfer plate to, for example, anepoxy-laminate portion of the CCD housing (or to some other thermallyinsulated structure or material) may prevent heating of the aluminumportion of the housing, and may minimize or eliminate re-circulation ofheat generated by the TEC back to the CCD or to the cavity in which itis disposed. Coupling the transfer plate to a heat sink (block 405)provides necessary cooling of the hot side of the TEC as indicated atblock 406.

The cooling operation depicted at block 406 may generally include orcomprise various cooling techniques generally known in the art ordeveloped and operative in accordance with known principles. In theexemplary embodiments, for example, cooling may include circulating(such as by fans or fan assemblies) ambient or cooled air across heatexchange fins on a heat sink. Those of skill in the art will appreciatethat some applications may employ a liquid cooled heat sink, forexample, or other structures and methods configured and operative tomaintain the hot side of the TEC at an appropriate operatingtemperature.

The FIG. 4 embodiment is presented for illustrative purposes only, andis not intended to imply an order of operations to the exclusion ofother possibilities. By way of specific example, the operations depictedat blocks 401 and 402 may be combined, for instance, or a spacer may beomitted substantially as set forth in detail above (i.e., in somestructural arrangements, the CCD may be coupled directly to the coldside of the TEC). Additionally, a method such as depicted in FIG. 4 mayfurther comprise selectively applying a conformal coating to thetransfer plate, the thermal barrier, the interface between thosecomponents, or some combination thereof. As set forth above, such acoating may provide an environmentally tight moisture barrier preventingdegradation of imaging characteristics and damage to electricalcomponents.

Those of skill in the art will appreciate that the particular sequencein which the operations depicted at blocks 401-406 are conducted may beinfluenced by, among other factors, the functionality and structuralconfiguration of a particular CCD apparatus, the intended operationalcharacteristics of the apparatus, or both.

The present invention has been illustrated and described in detail withreference to particular embodiments by way of example only, and not byway of limitation. Those of skill in the art will appreciate thatvarious modifications to the exemplary embodiments are within the scopeand contemplation of the present disclosure.

1. A method of cooling a charge-coupled device; said method comprising:coupling said charge-coupled device to a cold side of a thermoelectriccooling device; coupling a hot side of said thermoelectric coolingdevice to a transfer plate; mounting said transfer plate to a thermalbarrier, said thermal barrier defining a cavity thermally isolated fromsaid transfer plate, said cavity being adapted to house saidcharge-coupled device; and coupling said transfer plate to a heat sink.2. The method of claim 1 further comprising interposing a spacer betweensaid charge-coupled device and said cold side of said thermoelectriccooling device.
 3. The method of claim 2 wherein said interposingcomprises selectively dimensioning said spacer to maximize a surfacearea of contact between said charge-coupled device and said cold side ofsaid thermoelectric cooling device.
 4. The method of claim 2 whereinsaid interposing comprises selectively dimensioning said spacer toposition said hot side of said thermoelectric cooling device in apredetermined location relative to said charge-coupled device.
 5. Themethod of claim 1 further comprising selectively applying a conformalcoating to at least one of said transfer plate, said thermal barrier,and an interface between said transfer plate and said thermal barrier.6. The method of claim 5 wherein said selectively applying comprisesproviding an environmentally tight moisture barrier with said conformalcoating.
 7. The method of claim 1 further comprising cooling said hotside of said thermoelectric cooling device.
 8. The method of claim 7wherein said cooling comprises transferring heat generated by saidthermoelectric cooling device from said charge-coupled device.
 9. Themethod of claim 1 wherein said mounting comprises attaching saidtransfer plate to an epoxy laminate material.
 10. The method of claim 1wherein said mounting comprises isolating heat generated by saidthermoelectric cooling device from said charge-coupled device.
 11. Anapparatus comprising: a charge-coupled device mounted in a housing, saidhousing including a thermal barrier and a cavity for mounting saidcharge-coupled device; a thermoelectric cooling device having a coldside and a hot side; said cold side coupled to said charge-coupleddevice; a heat sink; and a transfer plate coupling said hot side of saidthermoelectric cooling device to said heat sink in a heat transferrelationship; said transfer plate mounted to said thermal barrier suchthat heat transfer between said thermoelectric cooling device and saidhousing is inhibited.
 12. The apparatus of claim 11 further comprising aspacer interposed between said charge-coupled device and said cold sideof said thermoelectric cooling device.
 13. The apparatus of claim 12wherein said spacer is selectively dimensioned to maximize a surfacearea of contact between said charge-coupled device and said cold side ofsaid thermoelectric cooling device.
 14. The apparatus of claim 12wherein said spacer is selectively dimensioned to position said hot sideof said thermoelectric cooling device in a predetermined locationrelative to said charge-coupled device.
 15. The apparatus of claim 11further comprising a conformal coating applied to at least one of saidtransfer plate, said thermal barrier, and an interface between saidtransfer plate and said thermal barrier.
 16. The apparatus of claim 15wherein said conformal coating provides an environmentally tightmoisture barrier.
 17. The apparatus of claim 11 wherein saidthermoelectric cooling device is a Peltier cooling device.
 18. Theapparatus of claim 11 wherein said transfer plate is constructed of aheat-conducting metal.
 19. The apparatus of claim 11 wherein saidthermal barrier is constructed of an epoxy laminate material.
 20. Theapparatus of claim 12 wherein said spacer is constructed of aheat-conducting metal.
 21. A method of cooling a charge-coupled device,said method comprising: providing a cavity in a housing, said cavityadapted to house said charge-coupled device; coupling saidcharge-coupled device to a cold side of a thermoelectric cooling device;coupling a hot side of said thermoelectric cooling device to a transferplate; sealing said cavity, said sealing operable to provide asubstantially environmentally-tight moisture barrier for saidcharged-coupled device; and interposing a thermal barrier between saidhousing and said transfer plate wherein said interposing comprisesisolating heat generated by said thermoelectric cooling device from saidcharged-coupled device.
 22. The method of claim 21 further comprisinginterposing a spacer between said charge-coupled device and said coldside of said thermoelectric cooling device.
 23. The method of claim 22wherein said interposing spacer between said charge-coupled device andsaid cold side of said thermoelectric cooling device comprisesselectively dimensioning said spacer to maximize a surface area ofcontact between said charge-coupled device and said cold side of saidthermoelectric cooling device.
 24. The method of claim 22 wherein saidinterposing spacer between said charge-coupled device and said cold sideof said thermoelectric cooling device comprises selectively dimensioningsaid spacer to position said hot side of said thermoelectric coolingdevice in a predetermined location relative to said charge-coupleddevice.
 25. The method of claim 21 further comprising cooling said hotside of said thermoelectric cooling device.
 26. The method of claim 25wherein said cooling comprises transferring heat generated by saidthermoelectric cooling device from said charge-coupled device.
 27. Themethod of claim 21 wherein said sealing comprises applying a conformalcoating.
 28. The method of claim 21 wherein said sealing is operable toprevent moisture from penetrating said cavity.
 29. The method of claim21 wherein said thermal barrier is constructed of an epoxy laminatematerial.
 30. An apparatus comprising: a housing having a cavity definedtherein, said cavity operative to mount a charge-coupled device; athermoelectric cooling device having a cold side and a hot side, saidcold side coupled to said charge-coupled device; a heat sink; a transferplate coupling said hot side of said thermoelectric cooling device tosaid heat sink in a heat transfer relationship; and a conformal coating,said conformal coating operable to provide a substantiallyenvironmentally tight barrier for said charge-coupled device and toinhibit penetration of said cavity by moisture.
 31. The apparatus ofclaim 30 further comprising a spacer interposed between saidcharge-coupled device and said cold side of said thermoelectric coolingdevice.
 32. The apparatus of claim 31 wherein said spacer is selectivelydimensioned to maximize a surface area of contact between saidcharge-coupled device and said cold side of said thermoelectric coolingdevice.
 33. The apparatus of claim 31 wherein said spacer is selectivelydimensioned to position said hot side of said thermoelectric coolingdevice in a predetermined location relative to said charge-coupleddevice.
 34. The apparatus of claim 30 wherein said thermoelectriccooling device is a Peltier cooling device.
 35. The apparatus of claim30 wherein said transfer plate is constructed of a heat-conductingmetal.
 36. The apparatus of claim 30 further comprising a thermalbarrier interposed between said housing and said transfer plate.
 37. Theapparatus of claim 36 wherein said thermal barrier is constructed of anepoxy laminate material.
 38. The apparatus of claim 36 wherein saidthermal barrier is interposed such that heat generated by saidthermoelectric cooling device is substantially isolated from saidcharged-coupled device.